Java tutorial
/* * Copyright 2014 Jakub Jirutka <jakub@jirutka.cz>. * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ package cz.jirutka.spring.http.client.cache; import net.jcip.annotations.ThreadSafe; import org.springframework.cache.Cache; import org.springframework.cache.support.SimpleValueWrapper; import org.springframework.util.Assert; import java.util.LinkedHashMap; import java.util.Map; /** * Simple LRU {@link Cache} implementation with adjustable capacity limit * based on {@link LinkedHashMap} from JDK. */ @ThreadSafe public class SynchronizedLruCache implements Cache { public static final int DEFAULT_INITIAL_CAPACITY = 16; public static final float DEFAULT_LOAD_FACTOR = 0.75f; private final String name; private final int capacity; private final LinkedHashMap<Object, ValueWrapper> store; /** * Create a new instance with default initial capacity and load factor. * * @param name An arbitrary name of this cache instance. * @param capacity The maximal capacity. */ public SynchronizedLruCache(String name, int capacity) { this(name, capacity, DEFAULT_INITIAL_CAPACITY > capacity ? capacity : DEFAULT_INITIAL_CAPACITY, DEFAULT_LOAD_FACTOR); } public SynchronizedLruCache(String name, int capacity, int initialCapacity, float loadFactory) { Assert.hasText(name, "name should not be blank"); Assert.isTrue(capacity > 0, "capacity must be greater then 0"); this.name = name; this.capacity = capacity; this.store = new LinkedHashMap<Object, ValueWrapper>(initialCapacity, loadFactory, true) { protected boolean removeEldestEntry(Map.Entry eldest) { return this.size() > SynchronizedLruCache.this.capacity; } }; } public String getName() { return name; } public Map getNativeCache() { return store; } public synchronized ValueWrapper get(Object key) { return store.get(key); } public synchronized void put(Object key, Object value) { Assert.notNull(value, "value must not be null"); store.put(key, createEntry(value)); } public synchronized void evict(Object key) { store.remove(key); } public synchronized void clear() { store.clear(); } protected ValueWrapper createEntry(Object value) { return new SimpleValueWrapper(value); } }